Why won't my Pokemon keep their nicknames when they go through Pokemon bank?

Question

I had a roggenrola named avalanche and it changed back to roggenrola

Answer 1

The names of unnicknamed Pokémon will be rechecked upon transfer, leading into foreign Pokémon to revert to the species name in their origin language if they had obtained a name of another origin by evolution and Pokémon from before Generation V to have their all-uppercase names updated to be capitalized normally. If a Pokémon's nickname contains a word which is prohibited in the Generation VI games, the Pokémon's nickname will be erased, reverting to the default species name.

Source

After researching further it may be because Avalanche has the following words in it's name:

Ava- Ava is an Italian word, it basically means "to f***" in English.

Ala- Ala is a French word used to describe a male individual, the word in English means "b****d" or "backstabber".

Source

Comments

got my vote :P

Answer 2

During transfer, the nicknames or OT names of your Pokemon will be
erased if they contain words prohibited from use on the Nintendo 3DS
system because they may be offensive to others.

so "avalanche" is a bad word somewhere. not really important where